The influential chairman of the Senate Foreign Relations Committee, Bob Corker, is worried that the US is ceding too much in its negotiations with Iran.

So worried that he's suggesting the US pull out of the deal if what he calls "the erosion" continues. He is particularly concerned about the inspections clauses in the deal. He says he's hearing (though when I pushed him he wouldn't say from whom) that the right to inspections of Iran's nuclear facilities anytime, anywhere, may be diluted.

He also points to redlines that have already been crossed, highlighting the fact that the deal has gone from being a 20-year agreement to a 10-year agreement, and that Iran's nuclear arrangements can be dismantled in country, not out of country.

Mr Corker told me he still wants a deal, and sees that as the best option for America. But the man who guided the Senate to a bill that gave overwhelming support the negotiations now sounds more sceptical.

A couple of hundred years ago, give or take a few decades, Americans chucked the Brits out, mostly because of taxes, but also partly to get rid of dynastic monarchy. That is why Jeb Bush is so keen to say he's far more than the brother and son of former presidents. He is, wait for it, his own man.

China's recent expansion in the South China Sea has drawn former enemies - the US and Vietnam - closer together

There is a delicious irony about a US defence secretary admiring the ranks of the Vietnamese military. Forty years after America suffered a humiliating defeat at the hands of the Vietcong, Ashton Carter was here to offer support to the former enemy.

And as is so often the case in global affairs, it is a friendship forged by a common foe.

Senator George Mitchell is good at negotiating - except with his wife.

When it came to choosing a place to live, Maine (his choice), New York (hers), the master negotiator lost the debate. Mr Mitchell joined me earlier to discuss his new memoir and rest assured we did get beyond how to deal with your spouse.

China has no need to be concerned by the new security pact between Japan and America - at least that's the optimistic view of Tom Schieffer, the former US Ambassador to Tokyo.

Mr Schieffer insists that the region is safer when Japan and the US are working closely together. He also says that people (i.e. the pesky reporters at the White House press conference today) should stop asking Prime Minister Abe to apologise for Japan's actions in WW2.

The commander of the USS Cole - the American warship bombed by al-Qaeda in Yemen in 2000 - tells me that right now the influence of the Iranian-backed Houthi rebels in Yemen could be more of a problem than al-Qaeda in the Arabian Peninsula.

Commander Kirk Lippold warned of Iran trying to send more weapons to the Houthis and of Iran gaining influence over the two choke points of the Middle East - at the mouth of the Red Sea and in the Straits of Hormuz.

Former US treasury secretary Hank Paulson thinks some Americans are naïve to assume that the Chinese government can do whatever it wants to grow its economy.

He believes there's more danger in exaggerating China's strength than in underestimating it, but he also concedes that America's economic prowess took a real hit in the eyes of the Chinese at the time of the 2008 crash - when Mr Paulson was running the US Treasury.

About Katty

Katty's career with the BBC began in Zimbabwe in 1990 where she filed radio reports for the Africa Service of BBC World Service radio.

She went on to work as a BBC correspondent in London, and later Tokyo.

She settled in Washington in 1996 where she took some time out of broadcast journalism to join The Times Washington bureau before returning to the BBC in 2002.

From Washington, Katty has covered sex scandals in the Clinton administration, three Presidential elections as well as wars in Kosovo, Afghanistan and Iraq.

She was at the Pentagon just 20 minutes after a hijacked plane flew into the building on 11 September 2001 - one of her most vivid journalistic memories is of interviewing soldiers still visibly shaking from the attack.

She is the co-author of the New York Times best seller Womenomics.

Katty grew up all over the Middle East, where her father was posted as a British diplomat.

She studied modern languages at Oxford and is a fluent French and Italian speaker with some "rusty Japanese".

Katty juggles her journalism with raising four children with her husband, a consultant.